The reason I put this in the China Shop was so that it could be batted around and argued about. I do not like tools I know are inaccurate, and I can guestimate chlorine usage just as quickly and accurately with the Rule of Thumb--and I don't need to be near a computer to do it. I can estimate MORE accurately with just a calculator even on a cell phone.

This is not a statistical error. That would be simply noise and of no concern. It is a systemic error which is a whole 'nother kettle of fish.

The Pool Calculator generates other recommendations, including amounts of Borax and other additives. What is the accuracy of THOSE estimates?

I am reminded of Doc Brown's 2 story tall ice machine that makes one cube of ice.

Remember: The China Shop is for arguing. If you don't want to, you don't have to.

Enjoy swimming with your dogs (BTW, they are something like 30x dirtier than a person who gets in your pool. So 2 dogs is like a load of 60 bathers) (according to our vet who does water-therapy for dogs).

Carl